Remove Duplicate Lines Online Free

Common use cases for removing duplicate lines

🔑 Keywords lists — remove duplicate keywords from SEO lists or ad groups
📧 Email lists — deduplicate mailing list exports
🗂️ Data cleaning — remove repeated entries from CSV exports
💻 Code logs — clean repeated log messages
📋 To-do lists — remove accidentally duplicated tasks
🌐 URL lists — deduplicate link collections

How it works

Text is split on newlines. Each line is trimmed and compared case-sensitively using a JavaScript Set. The first occurrence of each unique line is kept; all subsequent duplicates are discarded. The result is output in original order.

🗃️ Deduplicate Lines →

Frequently Asked Questions

Is the duplicate check case-sensitive?

Yes. "Hello" and "hello" are treated as two different lines. If you want case-insensitive deduplication, first convert to lowercase using the UPPERCASE/lowercase buttons, then run Remove Duplicate Lines.

Are blank lines considered duplicates?

Blank lines (empty or whitespace-only) are treated like any other line. Multiple consecutive blank lines will be reduced to one. If you want to remove all blank lines entirely, use the "Remove Empty Lines" button instead.

How many lines can I process?

No hard limit. The deduplication uses a JavaScript Set for O(n) performance — even lists with 100,000+ lines process in milliseconds on a modern device.